Echo PB-500T won’t start properly

[Cfs]

I have a PB-500T. Serial P31212136027
I can get it to start if I pour a small quantity of gas into the carb. After it starts it runs great full throttle and low idle. If I do not pour gas into the carb I can prime the carb ( a dozen pumps or more..full choke and pull, pull and pull some more and it never even pops. I gave pulled the spark plug after and it seems dry. What am I missing? This is a Walbro WAL-1 carb. It has the odd horizontal air valve on top of the carb. I have very little experience with this style of carb.

I have spark and I have 115 lbs of compression and it runs great once it starts. It seems like the gas isn’t getting into the cylinder. I replaced the fuel line and fuel filter, I replaced the coil and this problem is with a new aftermarket carb which did not correct the same issue as the original Echo/Walbro carb.

Could I gave an aid leak somewhere?
Any ideas greatly appreciated
CFS

 

[StarTech]

I have a PB-500T. Serial P31212136027

This is a Walbro WAL-1 carb. It has the odd horizontal air valve on top of the carb. I have very little experience with this style of carb.

It is what is called a choke. It is used to start the engine when it is cold. Close it and try starting the engine.

Now the little lever which is red or orange does tend to get broken off.

 

[Cfs]

It has a choke lever on the air filter box. The part on top of the carb echo calls an air valve assembly and it opens and closes via a link based on the throttle position and it fits into another part called a valve assembly. This 2nd valve asby is attached to the cylinder and 2 air hoses run from it to 2 parts identified as reed plates… inner and outer. I assume that the gas mixed with air is pulled through the carb and the valve assemblies through the reed plates and into the cylinder. I would was able to download an IPL of my model and have access to part numbers etc. however I am lacking the experience to trouble shoot the problem and I do not want to just throw parts at it. I can try to start it without choking it and see if that does anything. But as I detailed earlier the plug is not wet after failing to start with the choke on. I do not see the problem as too much fuel, more too little or no fuel. I am wondering if the reed asbys are gummed up and not openining like they should or if an air leak on the cylinder or crankshaft seals are reducing the pressure that needs to be exerted onto the reeds gat is needed to draw fuel into the cylinder. Especially when cranking by hand, maybe once it is firings and thus running at operating speed/rpm’s, and that higher pressure opens the reeds and it can continue to run
Hopefully someone has had a similar problem
CFS

 

[Cfs]

It has a choke lever on the air filter box. The part on top of the carb echo calls an air valve assembly and it opens and closes via a link based on the throttle position and it fits into another part called a valve assembly. This 2nd valve asby is attached to the cylinder and 2 air hoses run from it to 2 parts identified as reed plates… inner and outer. I assume that the gas mixed with air is pulled through the carb and the valve assemblies through the reed plates and into the cylinder. I would was able to download an IPL of my model and have access to part numbers etc. however I am lacking the experience to trouble shoot the problem and I do not want to just throw parts at it. I can try to start it without choking it and see if that does anything. But as I detailed earlier the plug is not wet after failing to start with the choke on. I do not see the problem as too much fuel, more too little or no fuel. I am wondering if the reed asbys are gummed up and not openining like they should or if an air leak on the cylinder or crankshaft seals are reducing the pressure that needs to be exerted onto the reeds gat is needed to draw fuel into the cylinder. Especially when cranking by hand, maybe once it is firings and thus running at operating speed/rpm’s, and that higher pressure opens the reeds and it can continue to run
Hopefully someone has had a similar problem
CFS

So I went to a local small engine shop who has a tech who really knows Echo. I was not able to speak directly to him since he was at lunch. The owner shuttled back and forth from the lunch table to the front counter and asked him about my problem. I brought my tablet with a pdf of the IPL for my model. They told me that the parts called reeds are really not reeds they are just hollow fittings that the fuel air mix can get to the cylinder through. They told me not to put the throttle on full, just take it off of the kill position, choke it via the small orange lever and pull the starter rope. They told me that setting it to high speed would prevent it from starting. So when I got home I did exactly what they told me and it would not start, in fact it never even popped. So I pulled the spark plug added about a tablespoon of gas ,replaced the plug choked it and it started on the 2nd or -3rd pull and it ran great. I shut it off and it restarted after 20-30 seconds. It would not start 5 mins later.

I think the tech refered to this Walbro YAL-1 carb as a dual barrel. There is a round opening with a brass throttle butterfly at the bottom of the carb and the valve above it has a horizontal l barrel that has a slot cut in it that as you engage the throttle more of the opening is opened for air to flow through.

It really seems like it is not getting enough gas to start. Either that or an air leak. it does have good Compression. Anybody have a similar issue that they found a fix for? Any and all ideas welcome

CFS

 

[StarTech]

Okay having to do some research in this end. Not able to find a Service manual via the net so I got try another source here but that takes several days and can come back nothing in the library.

Walbro WLA-1 Carb.

The reed valve assemblies are actual reed valves. Here is an image of one. Someone doesn't know what they are talking about.

The Walbro WLA-1 carburetor is a scavenger style carb. It is a design I haven't seen here as most of the ones I see here are the Zama versions which rotary barrel style. It allows additional air into the cylinder assy at mid and full position as to lean out the fuel mixture and to allow fresh air to replace the exhaust gases.

Check the intake gasket to make sure you didn't damage it, Check the cylinder to lower crankcase screws are good and tight. Another that can be checked without is seal off the intake and the two reed valve assemblies and do a pressure/vac test of the crankcase which checks for leaky oil seals the cylinder to crankcase gasket. IF the oil seals are leaking on vacuum or pressure they can cause lack fuel getting to the upper cylinder. It doesn't take much at times to cause problems. Btw lower crankcase air leaks does not affect the compression.

Crankcase screws are torque to 65-95 in lbs per the service data file. I usually use the higher end number.

As for reed valves they seldom ever give problems.

 

[Rivets]

Trying to teach someone how carbs work and troubleshoot them is difficult on a forum. We know what to do, but delivering that knowledge can be difficult. Maybe one of these sites will help you understand how Walbro carbs work and give you repair instructions.

https://www.rcgroups.com/forums/showatt.php?attachmentid=5145893&d=1347304698

http://www.baja5b.lv/wp-content/uploads/teh-info/Walbro%20Carburetor%20Theory.pdf

 

[StarTech]

I would link a service manual but every since Walbro changed up their site they just don''t keep things updated they use to do. The WLA is a newer design that they haven't release a service manual on.

older 2 Cycle Carbs...

Service Manuals - Walbro

All manual are in pdf format - Chainsaw Carburetors & Trimmer and Blower Carburetors.

www.walbro.com

 

[Cfs]

Thanks to everyone for their help! After talking with the Echo tech who had nothing good to say about aftermarket carbs; I purchased a k10-WLA rebuild kit and rebuilt the original Walbro WLA-1 carb with an actual Walbro kit. Lo and behold it fired up. It ran poorly and I was able to adjust it with a mini D tool. It seems to be running pretty darn goodnow!
I think I did not rebuild it correctly rdinitially and used the wrong pump diaphram. On that subject so many kits come with multiple pump diaphrams made of different materials. Is there some guidance on which one to use? I have always believed that the synthetic ones were the latest improved versions. Is that true?
The K10-WLA kit had 2 different rubber pump diaphrams and they were not identical but the only difference was the shape of the hole in the center...I just used the one that matched. I have always wondered what the different colors and materials are intended for. Anyone know??
CFS

 

[StarTech]

There is two versions of the K10-WLA kits. AN older version that has two different pump diaphragms and the latest with just one. Either way both kits are missing two parts that are in most kits, That is the metering lever and spring. Not a problem here as I save the new ones when the current lever is not worn.

But that what you got to do is to match the current gaskets used.

As for the kit since the newer kit is like the one on the right I would be ordering the CTS version as it is nearly third of the cost depending on which distributor I use. I just have to add it to my next order.

As to which material is better I simply haven't worried about it as I use what was used previously.

 

[Cfs]

I did think it was odd that the lever and spring were not included. I reused the old ones… not ideal. I was thinking that I had read somewhere that the synthetic pump diaphragms, like the electric blue colored one were an upgraded version and replaced earlier styles if they match are the pattern/configuration as the one you are replacing. I am going to try to research it at Walbro’s website